U.S. patent application number 15/196109 was filed with the patent office on 2018-01-04 for self-leveling mechanism and method for wheeled mobility device.
The applicant listed for this patent is UPnRIDE Robotics Ltd. Invention is credited to Amit GOFFER, Dudu HAIMOVICH, Roee HAIMOVICH, Oren TAMAR!.
Application Number | 20180001729 15/196109 |
Document ID | / |
Family ID | 60786955 |
Filed Date | 2018-01-04 |
United States Patent
Application |
20180001729 |
Kind Code |
A1 |
GOFFER; Amit ; et
al. |
January 4, 2018 |
SELF-LEVELING MECHANISM AND METHOD FOR WHEELED MOBILITY DEVICE
Abstract
A self-leveling mechanism for a mobility device, the mobility
device including a chassis configured to propel the mobility device
on a surface, includes a leveling structure on which is mounted a
user support for supporting a user of the mobility device. The
leveling structure is connected to the chassis by a swivel
connection that enables the leveling structure to swivel about the
connection, and by two linearly displaceable connections that are
laterally displaced from one another. Two linear actuators are each
configured to displace one of the displaceable connections to
adjust a distance between each displaceable connection and the
chassis. A sensor for senses a tilt of the leveling structure and a
controller is configured to operate the linear actuators in
accordance with the sensed tilt.
Inventors: |
GOFFER; Amit; (Kiryat Tivon,
IL) ; HAIMOVICH; Roee; (Migdal Haemek, IL) ;
TAMAR!; Oren; (Pardesia, IL) ; HAIMOVICH; Dudu;
(Ramat Yishai, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UPnRIDE Robotics Ltd |
Yokneam lllit |
|
IL |
|
|
Family ID: |
60786955 |
Appl. No.: |
15/196109 |
Filed: |
June 29, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60G 2300/24 20130101;
A61G 5/122 20161101; B60G 7/001 20130101; B60G 2400/0511 20130101;
A61G 2203/42 20130101; B60G 2800/01 20130101; A61G 2203/14
20130101; A61G 2203/44 20130101; B60G 2400/0512 20130101; B60G
2800/012 20130101; A61G 2203/30 20130101; B60G 2400/051 20130101;
A61G 5/128 20161101; B60G 2202/413 20130101; B60G 17/01908
20130101; A61G 2203/36 20130101; B60G 2800/014 20130101; A61G 5/14
20130101; B60G 2202/42 20130101; B60G 7/005 20130101; A61G 5/1048
20161101; A61G 2203/18 20130101; A61G 2203/16 20130101; A61G 5/042
20130101 |
International
Class: |
B60G 17/019 20060101
B60G017/019; B60G 7/00 20060101 B60G007/00 |
Claims
1. A mobility device comprising: a chassis configured to propel the
mobility device on a surface; and a self-leveling mechanism, the
self-leveling mechanism including: a leveling structure on which is
mounted a user support for supporting a user of the mobility
device, the leveling structure being connected to the chassis by a
swivel connection that enables the leveling structure to swivel
about the connection and by two linearly displaceable connections
that are laterally displaced from one another; two linear
actuators, each of the linear actuators configured to displace a
displaceable connection of the two displaceable connections to
adjust a distance between each displaceable connection and the
chassis; a sensor for sensing a tilt of the leveling structure; and
a controller that is configured to operate the linear actuators in
accordance with a tilt that is sensed by the sensor.
2. The device of claim 1, wherein the swivel connection comprises a
rod end bearing.
3. The device of claim 1, wherein the swivel connection is located
at a nonzero fixed distance from a floor of the chassis.
4. The device of claim 1, wherein the displaceable connection is
located along an arm of the leveling structure.
5. The device of claim 4, wherein the displaceable connection is
located at a front end of the leveling structure and the two
displaceable connections are located at a rear end of the leveling
structure.
6. The device of claim 1, wherein the linear actuator comprises a
screw mechanism.
7. The device of claim 6, wherein the displaceable connection
comprises a ball swivel.
8. The device of claim 1, wherein each of the displaceable
connections is configured to be displaced by its linear actuator
substantially vertically.
9. The device of claim 1, wherein the sensor comprises an inertial
measurement unit.
10. The device of claim 1, wherein the sensor is configured to
measure a pitch angle and a roll angle of the leveling
structure.
11. The device of claim 10, wherein the controller is configured to
apply a control algorithm to calculate a displacement of one or
both of the displaceable connections in accordance with a deviation
of the measured pitch angle from a pitch angle of a target plane or
a deviation of the measured roll angle from a roll angle of the
target plane.
12. The device of claim 11, wherein the size of the calculated
displacement during a single iteration of the control algorithm
increases when the deviation increases and decreases when the
deviation decreases.
13. The device of claim 1, comprising a conversion mechanism to
change a configuration of the user support between a configuration
for supporting the user in a standing position and a configuration
for supporting the user in seated position.
14. A method of controlling a tilt of a user support of a mobility
device, the method comprising: receiving a sensed tilt of a
leveling structure on which the user support is mounted, the
leveling structure being connected to a chassis of the mobility
device by a swivel connection that enables the leveling structure
to swivel about the connection and by two linearly displaceable
connections that are laterally displaced from one another;
calculating a linear displacement of each of two displaceable
connections of the leveling structure that reduces a deviation of
the sensed tilt of the stabilizing structure from an orientation of
a target plane; and operating a linear actuator of each of the
displaceable connections to displace each of the displaceable
connections by the calculated displacement for that displaceable
connection.
15. The method of claim 14, wherein receiving the sensed tilt
comprises receiving a sensed pitch angle and a sensed roll
angle.
16. The method of claim 15, wherein the deviation of the sensed
tilt of the self-leveling structure from the orientation of the
target plane comprises a pitch angular deviation of the sensed
pitch angle from a pitch angle of a target plane and a roll angular
deviation of the sensed roll angle from a roll angle of the target
plane.
17. The method of claim 16, wherein calculating the linear
displacement comprises calculating a linear combination of a pitch
deviation distance calculated using the pitch angular deviation and
a roll deviation distance calculated using the roll angular
deviation.
18. The method of claim 17, wherein a calculation of the pitch
deviation distance comprises raising an absolute value of the pitch
angular deviation to a positive power or calculation of the roll
deviation distance comprises raising an absolute value of the roll
angular deviation to a positive power.
19. The method of claim 14, wherein operating an actuator of the
two linear actuators comprises controlling a speed of rotation of a
motor of the actuator.
20. A self-leveling mechanism for a mobility device, the mobility
device including a chassis configured to propel the mobility device
on a surface, the mechanism comprising: a leveling structure on
which is mounted a user support for supporting a user of the
mobility device, the leveling structure being connected to the
chassis by a swivel connection that enables the leveling structure
to swivel about the connection and by two linearly displaceable
connections that are laterally displaced from one another; two
linear actuators, each of the linear actuators configured to
displace a displaceable connection of the two displaceable
connections to adjust a distance between each displaceable
connection and the chassis; a sensor for sensing a tilt of the
leveling structure; and a controller that is configured to operate
the linear actuators in accordance with a tilt that is sensed by
the sensor.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to wheeled mobility devices.
More particularly, the present invention relates to a mechanism and
method for self-leveling of a user of a wheeled mobility
device.
BACKGROUND OF THE INVENTION
[0002] Various types of wheeled mobility devices may provide
mobility to a user whose mobility may be limited due to a temporary
or permanent physical condition. Temporary conditions may include
injury, trauma, illness, unconsciousness, or other conditions.
Permanent or long term conditions may include from paraplegia,
quadriplegia, multiple sclerosis (MS), amyotrophic lateral
sclerosis (ALS), and similar conditions
[0003] Various types of wheelchairs and wheeled mobility devices
may enable person to be moved about while sitting or reclining.
Where the user is conscious and is capable of exerting the arms and
hands, the user may propel the wheels of the wheelchair or wheeled
mobility devices without the assistance of another person. Various
motorized wheelchairs and carts may enable a user to move the
device by simply manipulating a control, with minimal exertion.
Some such motorized wheelchairs and carts, as well as non-motorized
wheelchairs, have been designed to shift the user from a seated to
a standing position, and vice versa. Some have been designed to
transport the user while either standing (only indoors) or seated,
generally on level surfaces.
SUMMARY OF THE INVENTION
[0004] There is thus provided, in accordance with an embodiment of
the present invention, a mobility device including a chassis
configured to propel the mobility device on a surface; and a
self-leveling mechanism, the self-leveling mechanism including: a
leveling structure on which is mounted a user support for
supporting a user of the mobility device, the leveling structure
being connected to the chassis by a swivel connection that enables
the leveling structure to swivel about the connection and by two
linearly displaceable connections that are laterally displaced from
one another; two linear actuators, each of the linear actuators
configured to displace a displaceable connection of the two
displaceable connections to adjust a distance between each
displaceable connection and the chassis; a sensor for sensing a
tilt of the leveling structure; and a controller that is configured
to operate the linear actuators in accordance with a tilt that is
sensed by the sensor.
[0005] Furthermore, in accordance with an embodiment of the present
invention, the swivel connection includes a rod end bearing.
[0006] Furthermore, in accordance with an embodiment of the present
invention, the swivel connection is located at a nonzero fixed
distance from a floor of the chassis.
[0007] Furthermore, in accordance with an embodiment of the present
invention, the displaceable connection is located along an arm of
the leveling structure.
[0008] Furthermore, in accordance with an embodiment of the present
invention, the displaceable connection is located at a front end of
the leveling structure and the two displaceable connections are
located at a rear end of the leveling structure.
[0009] Furthermore, in accordance with an embodiment of the present
invention, the linear actuator includes a screw mechanism.
[0010] Furthermore, in accordance with an embodiment of the present
invention, the displaceable connection includes a ball swivel.
[0011] Furthermore, in accordance with an embodiment of the present
invention, each of the displaceable connections is configured to be
displaced by its linear actuator substantially vertically.
[0012] Furthermore, in accordance with an embodiment of the present
invention, the sensor includes an inertial measurement unit.
[0013] Furthermore, in accordance with an embodiment of the present
invention, the sensor is configured to measure a pitch angle and a
roll angle of the leveling structure.
[0014] Furthermore, in accordance with an embodiment of the present
invention, the controller is configured to apply a control
algorithm to calculate a displacement of one or both of the
displaceable connections in accordance with a deviation of the
measured pitch angle from a pitch angle of a target plane or a
deviation of the measured roll angle from a roll angle of the
target plane.
[0015] Furthermore, in accordance with an embodiment of the present
invention, the size of the calculated displacement during a single
iteration of the control algorithm increases when the deviation
increases and decreases when the deviation decreases.
[0016] Furthermore, in accordance with an embodiment of the present
invention, the mechanism includes a conversion mechanism to change
a configuration of the user support between a configuration for
supporting the user in a standing position and a configuration for
supporting the user in seated position.
[0017] There is further provided, in accordance with an embodiment
of the present invention, a method of controlling a tilt of a user
support of a mobility device includes: receiving a sensed tilt of a
leveling structure on which the user support is mounted, the
leveling structure being connected to a chassis of the mobility
device by a swivel connection that enables the leveling structure
to swivel about the connection and by two linearly displaceable
connections that are laterally displaced from one another;
calculating a linear displacement, of each of two displaceable
connections of the leveling structure that reduces a deviation of
the sensed tilt of the stabilizing structure from an orientation of
a target plane; and operating a linear actuator of each of the
displaceable connections to displace each of the displaceable
connections by the calculated displacement for that displaceable
connection.
[0018] Furthermore, in accordance with an embodiment of the present
invention, receiving the sensed tilt includes receiving a sensed
pitch angle and a sensed roll angle.
[0019] Furthermore, in accordance with an embodiment of the present
invention, the deviation of the sensed tilt of the self-leveling
structure from the orientation of the target plane includes a pitch
angular deviation of the sensed pitch angle from a pitch angle of a
target plane and a roll angular deviation of the sensed roll angle
from a roll angle of the target plane.
[0020] Furthermore, in accordance with an embodiment of the present
invention, calculating the linear displacement includes calculating
a linear combination of a pitch deviation distance calculated using
the pitch angular deviation and a roll deviation distance
calculated using the roll angular deviation.
[0021] Furthermore, in accordance with an embodiment of the present
invention, a calculation of the pitch deviation distance includes
raising an absolute value of the pitch angular deviation to a
positive power or calculation of the roll deviation distance
includes raising an absolute value of the roll angular deviation to
a positive power.
[0022] Furthermore, in accordance with an embodiment of the present
invention, operating an actuator of the two linear actuators
includes controlling a speed of rotation of a motor of the
actuator.
[0023] There is further provided, in accordance with an embodiment
of the present invention, a self-leveling mechanism for a mobility
device including a chassis configured to propel the mobility device
on a surface, the mechanism including: a leveling structure on
which is mounted a user support for supporting a user of the
mobility device, the leveling structure being connected to the
chassis by a swivel connection that enables the leveling structure
to swivel about the connection and by two linearly displaceable
connections that are laterally displaced from one another; two
linear actuators, each of the linear actuators configured to
displace a displaceable connection of the two displaceable
connections to adjust a distance between each displaceable
connection and the chassis; a sensor for sensing a tilt of the
leveling structure; and a controller that is configured to operate
the linear actuators in accordance with a tilt that is sensed by
the sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order for the present invention, to be better understood
and for its practical applications to be appreciated, the following
Figures are provided and referenced hereafter. It should be noted
that the Figures are given as examples only and in no way limit the
scope of the invention. Like components are denoted by like
reference numerals.
[0025] FIG. 1A schematically illustrates a wheeled mobility device
configured to support a user in a sitting position, in accordance
with an embodiment of the present invention.
[0026] FIG. 1B schematically illustrates the wheeled mobility
device of FIG. 1A, configured to support a user in a standing
position.
[0027] FIG. 1C is a schematic block diagram of an electrical unit
of the wheeled mobility device shown in FIG. 1A.
[0028] FIG. 2A schematically illustrates a tiltable leveling
structure of a wheeled mobility device, in accordance with an
embodiment of the present invention.
[0029] FIG. 2B is a schematic oblique view from below of the
tiltable leveling structure shown in FIG. 2A.
[0030] FIG. 2C is a schematic enlarged view of a swivel connection
of the tiltable leveling structure shown in FIG. 2B.
[0031] FIG. 2D is a schematic top view of the tiltable leveling
structure shown in FIG. 2A.
[0032] FIG. 3A schematically illustrates operation of a tiltable
leveling structure of a wheeled mobility device, in accordance with
an embodiment of the present invention.
[0033] FIG. 3B schematically illustrates a cross-sectional view
along a lateral axis of the tiltable leveling structure shown in
FIG. 3A illustrating roll angle control.
[0034] FIG. 3C schematically illustrates a cross sectional view
along a longitudinal axis of the tiltable leveling structure shown
in FIG. 3A illustrating pitch angle control.
[0035] FIG. 4 is a flowchart depicting a method for controlling a
tiltable leveling structure of a wheeled mobility device, in
accordance with an embodiment of the present invention.
[0036] FIG. 5 is a block diagram of a control algorithm of the
method depicted in FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
[0037] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the invention. However, it will be understood by those of
ordinary skill in the art that the invention may be practiced
without these specific details. In other instances, well-known
methods, procedures, components, modules, units and/or circuits
have not been described in detail so as not to obscure the
invention.
[0038] Although embodiments of the invention are not limited in
this regard, discussions utilizing terms such as, for example,
"processing," "computing," "calculating," "determining,"
"establishing", "analyzing", "checking", or the like, may refer to
operation(s) and/or process(es) of a computer, a computing
platform, a computing system, or other electronic computing device,
that manipulates and/or transforms data represented as physical
(e.g., electronic) quantities within the computer's registers
and/or memories into other data similarly represented as physical
quantities within the computer's registers and/or memories or other
information non-transitory storage medium (e.g., a memory) that may
store instructions to perform operations and/or processes. Although
embodiments of the invention are not limited in this regard, the
terms "plurality" and "a plurality" as used herein may include, for
example, "multiple" or "two or more". The terms "plurality" or "a
plurality" may be used throughout the specification to describe two
or more components, devices, elements, units, parameters, or the
like. Unless explicitly stated, the method embodiments described
herein are not constrained to a particular order or sequence.
Additionally, some of the described method embodiments or elements
thereof can occur or be performed simultaneously, at the same point
in time, or concurrently. Unless otherwise indicated, the
conjunction "or" as used herein is to be understood as inclusive
(any or all of the stated options).
[0039] Some embodiments of the invention may include an article
such as a computer or processor readable medium, or a computer or
processor non-transitory storage medium, such as for example a
memory, a disk drive, or a USB flash memory, encoding, including or
storing instructions, e.g., computer-executable instructions, which
when executed by a processor or controller, carry out methods
disclosed herein.
[0040] In accordance with an embodiment of the present invention, a
wheeled mobility device includes a self-leveling mechanism that
includes a tiltable leveling structure. The self-leveling mechanism
may be operated to maintain the user of the wheeled mobility device
at a substantially constant orientation relative to an external
axis or plane, e.g., to the vertical or to the horizontal. As used
herein, leveling or self-leveling refers to maintaining an
orientation relative to a specified plane, whether or not the
specified plane is horizontal.
[0041] A user support for supporting a user of the wheeled mobility
device may be attached to the tiltable leveling structure. The
orientation of the user support may be fixed with respect to the
orientation of the tiltable leveling structure. For example, the
user support may include a seat or bed, a harness structure that is
configured to support the user in a standing position, or user
support structure that is configured to support the user in a range
of positions. For example, the user support may include a seat with
restraints with a conversion mechanism that is operable to raise
the user from a sitting position to a standing position, and vice
versa. One or more extendible columns or rods may straighten or
bend various hinges to convert a seat to a standing harness.
[0042] The tiltable leveling structure is connected to, or
otherwise supported by, a chassis of the wheeled mobility device
(e.g., via actuators and a rod end bearing, the rod end bearing
also known as a heim joint or rose joint). The chassis may include
or support a motorized propulsion mechanism for propelling the
wheeled mobility device along a surface. For example, the chassis
may include wheels or tracks that may be rotated or moved by the
motorized propulsion mechanism. For example, the motorized
propulsion mechanism may include an electric motor (e.g., powered
by a storage battery or otherwise), an internal combustion engine,
or another suitable motor.
[0043] A part of the tiltable leveling structure may be connected
to the chassis via a swivel connection, e.g., at or near an edge or
end of the tiltable leveling structure, e.g., along an arm of the
tiltable stabilizing structure. For example, the swivel connection
may be located near an end of an arm that extends forward
approximately along a longitudinal midline (e.g., that is
approximately midway between right and left sides of the tiltable
leveling structure) of the tiltable leveling structure. The swivel
connection to the chassis enables at least limited rotation about
at least two orthogonal axes (e.g., defining pitch and roll of the
tiltable stabilizing structure). For example, the joint may include
a ball joint, a rod end bearing, or another passive joint that
enables rotation about at least two axes.
[0044] As used herein, forward and backward longitudinal directions
of the wheeled mobility device or its components are defined with
reference to the orientation of a user that is being carried by the
wheeled mobility device in a manner for which the wheeled mobility
device is designed. In particular, the user is being supported by
the user support such that the user's back is supported by, or is
adjacent to, a back support panel of the user support. Right and
left lateral directions, as well as pitch and roll of the likable
leveling structure of the user support, are similarly defined.
[0045] For example, the swivel connection may be located on an arm
of the tiltable leveling structure. For example, the arm may extend
forward from the remainder of the tiltable leveling structure. The
arm may include structure (e.g., bar or rod) that may pass through
the opening of a rod end bearing whose shaft is fixed to chassis to
form the swivel connection. For example, the shaft of the rod end
bearing may rise approximately vertically from a floor (or other
part) of the chassis such that the swivel connection is located at
a nonzero fixed distance above the floor of the chassis.
Alternatively, the arm, or other structure of the tiltable leveling
structure, may otherwise connect to the chassis to form the swivel
connection
[0046] Two actuator assemblies are each configured to substantially
linearly vertically displace one of two displaceable connections of
the tiltable leveling structure. The two displaceable connections
are laterally displaced (by the actuator) from one another and from
the swivel connection. In some cases, the two displaceable
connections may be vertically displaced relative to one another or
relative to the swivel connection when the wheeled mobility device
is resting on a level horizontal surface and the tiltable leveling
structure is also oriented parallel to the surface. For example,
each linear actuator may be operable to substantially linearly
displace the displaceable connection of the tiltable leveling
structure in the vertical direction. Thus, operation of each
actuator may adjust a distance between its corresponding
displaceable connection and a floor of the chassis. For example,
the actuator may include a screw mechanism, a scissors mechanism,
or eccentric disk mechanism, a hydraulic or pneumatic piston, or
another suitable mechanism for effecting a substantially vertical
displacement. The operation of the two linear actuators may cause
the tiltable leveling structure to rotate relative to the swivel
connection around one or more axes. Typically, operation of the two
actuators may change a pitch angle, roll angle, or both or another
angle, of the tiltable leveling structure.
[0047] The positions of the swivel connection and the displaceable
connections may be selected to provide a predetermined degree of
control or mechanical advantage. For example, mutual separation
distances among the swivel connection and the displaceable
connections may be selected to be as large as possible (e.g.,
within constraints that may be imposed by structure of the chassis,
of the tiltable leveling structure, or of structure that is
attached to the chassis or the tiltable leveling structure). For
example, if the swivel connection is located on a forward extending
arm near a lateral midline of the tiltable stabilizing structure,
then the displaceable connections may be located near opposite
corners at the rear edge of the tiltable leveling structure. The
mutual lateral separations among the swivel connection and the
displaceable connections may be selected such that the separation
distance is large enough so as not to require excessive thrust by
the actuator, while being small, enough so as to enable
sufficiently rapid tilting of the self-leveling structure.
[0048] One or more sensors may be configured to sense a tilt of the
tiltable leveling structure with respect to the horizontal or
another predetermined plane. The sensors may be fixed to structure
that is fixed to the tiltable leveling structure so as to tilt
together with the tiltable leveling structure.
[0049] For example, the sensors may be configured to measure roll
and pitch angles of the tiltable leveling structure relative to a
target plane. The sensors may include one or more inertial
measurement units, tilt sensors, or other sensors that may be
configured to measure a tilt of the tiltable leveling structure
with respect to a predetermined plane. For example, an inertial
measurement unit may include one or more gyroscopes,
accelerometers, fused gyro-accelerometers, inclinometers or tilt
sensors, or other sensors capable of measuring or sensing an
orientation, a change in orientation, a rate of change in
orientation, or other quantities that may be interpreted to yield a
current roll or pitch angle or other indicators of a tilt.
[0050] One or more surface tilt sensors may be mounted on the
chassis to measure the tilt of a surface upon which the device is
moving or standing. The measured surface tilt may be utilized to
limit the dynamic range of the self-leveling mechanism. For
example, when the wheeled mobility device is balanced and stable,
the balance sensors output the target pitch and roll angles; by
comparing to the measured surface-slope angles, the amount of tilt
correction, done by the balancing mechanism, can be computed and
hence alerting when the dynamic angles-correction range exceeds its
permitted limits. Second, warn the system (and user) for hazardous
slopes.
[0051] A controller of the wheeled mobility device may be
configured to operate the actuators to maintain the tilt of the
tiltable leveling structure substantially parallel to a
predetermined target plane. For example, the target plane may be
horizontal (characterized by zero pitch and roll angles). In some
cases, another target plane may be selected. For example, a
particular user of the wheeled mobility device may feel more
comfortable when, or otherwise prefer, leaning slightly backward,
forward, or sideways when being carried by the wheeled mobility
device.
[0052] The controller may apply an iterative algorithm to operate
the actuators in accordance with measured tilts. For example, in
each iteration of the algorithm, a current tilt (e.g., roll and
pitch) of the tiltable leveling structure may be measured. A
deviation of the measured tilt from the orientation of the target
plane may be calculated.
[0053] A function of the deviation in each angle (e.g., roll and
pitch) may be applied to yield a correction step that includes a
displacement along a straight line that is to be applied to correct
the measured deviation. The function may be configured such that
step size is proportionally larger (e.g., as expressed as a ratio
of step size to angular deviation) for large deviations than it is
for smaller deviations. For example, the function may include
raising the deviation to a nonzero power. Parameters of the
function may be determined by a technician and may depend on such
factors as geometry of the tiltable stabilizing structure,
properties of the actuators, or other factors.
[0054] The calculated displacement correction steps may be used to
calculate a (e.g., vertical) displacement of each of the
displaceable connections. A speed of operation of each of the
actuators may be calculated such that the calculated displacement
is achieved during the iteration. Each actuator may then be
operated at the calculated speed of operation (e.g., controlled by
controlling the voltage that is applied to the actuator, or by
controlling the duty-cycle of pulse-width-modulation (PWM) that is
applied to the actuator) in order to achieve the calculated
displacement.
[0055] An iteration control method as described herein may be
advantageous over other types of control methods (e.g.,
proportional-integral-derivative, or PID, control). For example,
the control method described herein may result in less overshoot,
and less sensitivity to motor backlash or other mechanical
inaccuracies than other control methods. Thus, the control method
described herein may enable sufficiently fast convergence of the
tilt of the tiltable leveling structure to the target plane to
ensure the comfort and safety of the user. Furthermore, an
iterative control method as described herein is independent of
dynamic parameters of the system, and thus does not require a
priori knowledge of these dynamic parameters. For example, the
iterative control method is independent of such dynamic parameters
as mass of components, moments of inertia, and applied forces
(within ranges derived from systems specifications).
[0056] FIG. 1A schematically illustrates a wheeled mobility device
configured to support a user in a sitting position, in accordance
with an embodiment of the present invention. FIG. 1B schematically
illustrates the wheeled mobility device of FIG. 1A, configured to
support a user in a standing position.
[0057] Wheeled mobility device 10 includes chassis 11. Chassis 11
includes a chassis floor 24 and one or more wheels (or tracks or
other structure) for enabling self-propelled travel by wheeled
mobility device 10 over a surface (e.g., a floor, road, sidewalk,
driveway, ramp, or other surface suitable for self-propelled
travel). For example, chassis 11 may include one or more drive
wheels 22. Each drive wheel 22 may be connected to a wheel drive
23. For example, wheel drive 23 may include a drive motor, a
transmission, or both. A drive motor may include an electric motor,
an internal combustion engine, or another suitable type of motor or
engine. Chassis 11 may include one or more support wheels 26.
Support wheels 26 may include non-driven wheels that provide stable
support for wheeled mobility device 10 (e.g., such that the total
number of wheels, including drive wheels 22 and supports wheels 26,
is at least three, e.g., at least four with two drive wheels 22 and
two support wheels 26). For example, swivel wheels 26 may be
connected to chassis 11 by bearings that enable support wheels 26
to swivel freely so as to provide support without impeding movement
of wheeled mobility device 10.
[0058] In wheeled mobility device 10 as shown in FIGS. 1A and 1B,
swivel wheels 26 are located at the rear of the device.
Alternatively, swivel wheels 26 may be located at the front of the
device while drive wheels 22 may be located at the rear. As another
example, drive wheels 22 may be located near the center chassis 11
with two sets of swivel wheels 26, e.g., one set being located at
the front of wheeled mobility device 10, and the other at the
rear.
[0059] In some cases, steering of wheeled mobility device 10 may be
achieved by separate control of speeds of rotation of two different
support wheels 26. In some cases, the speed of rotation may be
controlled by controlling a voltage that is applied to a motor of
wheel drive 23 (e.g., via electrical unit 20). For example,
rotating one of drive wheels 22 more rapidly about its axis (e.g.,
axle) than the other drive wheel 22 may turn wheeled mobility
device 10 toward the more slowly rotating drive wheel 22. In other
cases, wheel drive 23 of may be configured to rotate one or more
drive wheels 22 about a vertical axis in order to steer wheeled
mobility device 10.
[0060] Operation of drive wheels 22 may be controlled by a user
that is riding wheeled mobility device 10, or another user, by
operating user controls 34 (e.g., via electrical unit 20). For
example, user controls 34 may include one or more joysticks,
pushbuttons, switches, levers, keyboards, keypads, pointing
devices, touch screens, head movement sensors, or other controls.
Some or all of user controls 34 may be mounted on wheeled mobility
device 10 (e.g., on an armrest or elsewhere) so as to be
conveniently accessible by a user of wheeled mobility device 10. In
some cases, some or all of user controls 34 may be located on a
remote device, e.g., so as to enable operation of user controls 34
by a user who is not currently riding wheeled mobility device
10.
[0061] User support 14 may include one or more components for
supporting a user in one or more of a sitting, standing, or other
position. For example, a back panel 30 of user support 14 may be
configured to support a user's back. Back panel 30 may serve as a
backrest of a seat 36 when wheeled mobility device 10 is configured
to support a user in a seated position (FIG. 1A). When wheeled
mobility device 10 is configured to support a user in a standing
position, back panel 30 may be harnessed to the user's back in
order to hold the upper body of the user in an upright orientation
(FIG. 1B). Similarly, when configured to support the user in an
upright position, seat 36 may be turned vertically and may be
harnessed to the user's midsection in order to support the
midsection in a standing position. A foot panel 32 may be
configured to support the user's feet when wheeled mobility device
10 is configured to support the user in both seated and standing
positions.
[0062] Support conversion mechanism 18 may be operated (e.g., a
motor of support conversion mechanism 18 operated in response to
operation of user controls 34 and operation of electrical unit 20)
to change a configuration of user support 14. Support conversion
mechanism 18 may include one or more motors, actuators, hinges, or
other components that may be operated to convert user support 14
from a seated configuration to a standing configuration, and vice
versa.
[0063] During operation of support conversion mechanism 18, one or
more panels of user support 14 may rotate or bend relative to
another. For example, seat 36, which is substantially horizontal
when user support 14 is in a seated configuration, may be rotated
to a substantially vertical orientation during conversion to a
standing configuration, and vice versa. A connector between panels
of user support 14, such as panel connection 35 between back panel
30 and seat 36, may be configured to enable one or both of the
connected panels to rotate. For example, panel connection 35 may be
made of a flexible material or may be hinged (or may be absent), so
as to enable seat 36 to rotate back-and-forth between a vertical
and a horizontal orientation during operation of support conversion
mechanism 18.
[0064] For example, support conversion mechanism 18 may include a
column or similar structure that may be extended (e.g., telescoped
outward) or retracted (e.g., telescoped inward), rotated, or both,
to raise or lower a support connection 37. For example, with user
support 14 in a seated configuration, raising support connection 37
may fold seat 36 inward from a horizontal to a vertical
orientation, may raise back panel 30, and may draw leg braces 33
and foot panel 32 proximally inward. Thus, support conversion
mechanism 18 may convert user support 14 to a standing position.
Similarly, with user support 14 in a standing configuration,
lowering support connection 37 may fold seat 36 outward from a
vertical to a horizontal orientation, may lower back panel 30, and
may extend leg braces 33 and foot panel 32 distally inward. Thus,
support conversion mechanism 18 may convert user support 14 to a
seated position.
[0065] Support conversion mechanism 18 and user support 14 may be
configured to maintain a center of gravity of wheeled mobility
device 10 in an approximately constant lateral and longitudinal
position relative to chassis 11. For example, the position of the
center of gravity may be maintained approximately above a position
of a geometric center of chassis 11 or a geographic center of the
wheels (e.g., drive wheels 22 and support wheels 26) of chassis
11.
[0066] User support 14 is mounted on tiltable leveling structure
12. Tiltable leveling structure 12 is configured to control an
orientation of user support 14. For example, tiltable leveling
structure 12 may be configured to maintain an orientation at an
orientation that is defined, e.g., with respect to the vertical or
horizontal. Tiltable leveling structure 12 may include one or more
displaceable connections 16 that are movable by actuators (e.g., as
controlled by electrical unit 20) to maintain the orientation of
user support 14.
[0067] Electrical unit 20 may include one or more components that
enable operation of electrical or electronic components of wheeled
mobility device 10. Components of electrical unit 20 may be located
in a single housing (as shown in FIGS. 1A and 1B, or may be located
in two or more separate housings at various locations).
[0068] FIG. 1C is a schematic block diagram of an electrical unit
of the wheeled mobility device shown in FIGS. 1A and 1B.
[0069] Electrical unit 20 may include a controller 19 and a power
source 21.
[0070] For example, power source 21 may include a storage battery,
another type of battery, a solar panel, a generator, a connection
to an external electrical power source (e.g., an electrical mains),
or another source of electrical power.
[0071] Controller 19 may include a processor 25. Processor 25 may
include one or more processing units or computers. Processor 25 may
be configured to operate in accordance with programmed
instructions.
[0072] Processor 25 may communicate with data storage 29. For
example, data storage 29 may include one or more fixed or
removable, volatile or non-volatile, remote or local, data storage
units, memories, or computer-readable media. For example, data
storage 29 may be utilized to store one or more of programmed
instructions for operation of processor 25, parameters or data that
are utilized in executing programmed instructions, or results of
execution of programmed instructions.
[0073] Processor 25 may be configured to operate in accordance with
one or more signals that are received from sensors 31. For example,
sensors 31 may include one or more sensors that are configured to
detect a tilt of a component of tiltable leveling structure 12 or
of user support 14. Sensors 31 may include one or more inertial
measurement units, tilt sensors, accelerometers, gyroscopes,
compasses, or other sensors that may be utilised to determine an
orientation (e.g., yaw, pitch, roll) of tiltable leveling structure
12, of user support 14, or of chassis 11. Sensors 31 may include
sensors for measuring the tilt or slope of a surface that supports
wheeled mobility device 10. Sensors 31 may include a magnetometer
or compass for measuring the orientation of mobility device 10
relative to the magnetic field of the Earth. Sensors 31 may include
sensors for measuring a speed of rotation of one or more wheels
(e.g., drive wheels 22 or support wheels 26). Sensors 31 may
include one or more navigation sensors for determining a geographic
position of wheeled mobility device 10. Sensors 31 may include
force sensors for measuring a current load (e.g., weight) supported
by wheeled mobility device 10, a charge level of a battery of power
source 21, an impact, detecting an obstacle, or other types of
sensors for detecting a potentially hazardous situation or other
information.
[0074] Processor 25 may be configured to operate in accordance with
control input that is received from one or more user controls 34.
For example, user controls 34 may be operated to indicate a desired
orientation or direction of travel of wheeled mobility device 10, a
desired speed of travel of wheeled mobility device 10, a desired
configuration of user support 14 (e.g., seated or standing), or
another indication of a command or preference by the user or
another user or operator of wheeled mobility device 10.
[0075] Controller 19 may include motor control 27. Processor 25 may
be configured to communicate with motor control 27 to control one
or more motors. Motor control 27 may include one or more
controllers that are each configured to control operation of one or
more motors. For example, a motor that is controlled by motor
control 27 may include a motor of a wheel drive 23, a motor of
support conversion mechanism 18, or an actuator 60 of tiltable
leveling structure 12. Processor 25 may be configured to apply one
or more algorithms to calculate an operation of the motors on the
basis of operation of user controls 34 and on the basis of one or
more quantities sensed by sensors 31.
[0076] FIG. 2A schematically illustrates a self-leveling mechanism
of a wheeled mobility device, in accordance with an embodiment of
the present invention. FIG. 2B is a schematic oblique view from
below of the self-leveling mechanism shown in FIG. 2A. FIG. 2C is a
schematic enlarged view of a swivel connection of a tiltable
leveling structure of the self-leveling mechanism shown in FIG. 2B.
FIG. 2D is a schematic top view of the self-leveling mechanism
shown in FIG. 2A.
[0077] Self-leveling mechanism 13 includes tiltable leveling
structure 12 and linear actuator assemblies 61. Linear actuator
assemblies 61 are operable by controller 19 to adjust a tilt of
tiltable leveling structure 12 in accordance with a tilt measured
by inertial measurement unit 40, or by another sensor of sensors
31.
[0078] Shaft 75 of rod-end bearing 74 may be fixed to chassis floor
24 of chassis 11. Swivel bar 72 is located near a distal end of arm
64 of tiltable leveling structure 12. Swivel bar 72 may connect to
(e.g., pass through a swivel opening 73 of) rod end bearing 74.
Shaft 75 holds the opening of rod-end bearing 74, and thus swivel
bar 72, at a fixed nonzero distance (e.g., with value H.sub.0)
above chassis floor 24. The connection to rod-end bearing 74 forms
swivel connection 28. Swivel connection 28 may thus enable at least
limited rotation of arm 64 and tiltable leveling structure 12
relative to shaft 75 and chassis 11. The fixed distance H.sub.0 may
be sufficient such that neither chassis floor 24 nor another
structure of chassis 11 interferes with tilting of tiltable
leveling structure 12 (within a predetermined range of tilt angles,
e.g., selected to be sufficient to enable self-leveling of user
support 14 when wheeled mobility device 10 travels over a surface
whose maximum slope is within a predetermined range of slope
angles). User support 14, including foot panel 32, is fixed to
tiltable leveling structure 12. Thus, swivel connection 28 may
enable sufficient tilting of user support 14 so as to maintain user
support 14 in an approximately constant orientation with respect to
the horizontal (typically constant roll and pitch angles with
respect to the horizontal).
[0079] Linear actuator assemblies 61 are each configured to
linearly displace one of displaceable connections 16a and 16b.
Actuator base 66 of each linear actuator assembly 61 may be fixed
to chassis floor 24. For example, each actuator 60 may be
configured to rotate an actuator shaft 62 with exterior threading.
Each of displaceable connections 16a and 16b may include connection
structure 63 that includes an opening, sleeve, or ring with
corresponding interior threading. For example, the internal
threading may be located in bore of ball swivel 65 of connection
structure 63. Ball swivel 65 may enable at least a limited change
in orientation of actuator shaft 62 relative to tilt plate 68 or
other structure of tiltable leveling structure 12. Thus, rotation
of actuator shaft 62 may displace displaceable connection 16a or
16b along actuator shaft 62 to increase or decrease a distance
between the displaceable connection 16a or 16b and chassis floor
24. In addition, actuator base 66 may be configured to enable
actuator shaft 62 and actuator 60 rotate or tilt relative to
chassis floor 24, to enable tiltable leveling structure 12 to tilt
relative to chassis floor 24.
[0080] Alternatively to linear actuator assembly 61, other
structures or mechanisms may be used, e.g., scissor-jack motors,
eccentric drives, a hydraulic mechanism, an electromagnetic
mechanism, or another mechanism. In some such alternatives,
displaceable connection 16a or 16b may be fixed to actuator shaft
62. For example, actuator shaft 62 may be extendible to increase a
distance between the corresponding displaceable connection 16a or
16b and chassis floor 24. Actuator shaft 62 may be retractable to
decrease the distance between the corresponding displaceable
connection 16a or 16b and chassis floor 24.
[0081] Each displaceable connection 16a or 16b is connected to an
end of tilt plate 68. Tilt plate 68 is fixed to arm 64 at junction
70. Thus, raising or lowering displaceable connections 16a and 16b
in tandem may raise or lower tilt plate 68 relative to swivel
connection 28. In the arrangement shown, with arm 64 extending
forward and displaceable connections 16a or 16b located at lateral
(right-left) ends of tilt plate 68, the raising or lowering may
change a pitch angle of arm 64, and thus of user support 14.
Raising or lowering one of displaceable connections 16a and 16b
relative to the other may change a lateral tilt of tilt plate 68.
In the arrangement shown, the raising or lowering of one of
displaceable connections 16a and 16b relative to the other may
change a roll angle of arm 64, and thus of user support 14.
Alternative orientations of arm 64 and of displaceable connections
16a and 16b relative to a direction of forward motion of wheeled
mobility device 10 (e.g., arm 64 extending backward or to one side,
with moveable points 16a and 16b being correspondingly located) may
be provided.
[0082] Tillable leveling structure 12 is provided with inertial
measurement unit 40, or another sensor of sensors 31, for measuring
a tilt of tiltable leveling structure 12. For example, inertial
measurement unit 40 may be mounted on arm 64 (as shown), on tilt
plate 68, on foot panel 32, or elsewhere on tiltable leveling
structure 12 or user support 14.
[0083] Processor 25 may be configured to control operation of
actuators 60 in accordance with tilt angles that are sensed by
inertial measurement unit 40 or by another type of sensor 31, or
that are calculated from quantities that are measured by inertial
measurement unit 40 or another sensor 31.
[0084] FIG. 3A schematically illustrates operation of a tiltable
leveling structure of a wheeled mobility device, in accordance with
an embodiment of the present invention. FIG. 3B schematically
illustrates a cross sectional view along a lateral axis of the
tiltable leveling structure shown in FIG. 3A, illustrating roll
angle control. FIG. 3C schematically illustrates a cross sectional
view along a longitudinal axis of the tiltable stabilizing
structure shown in FIG. 3A, illustrating pitch angle control.
[0085] For the sake of simplicity, tiltable stabilizing structure
12 is represented in FIGS. 3A-3C by a representative plane 57. When
tiltable stabilizing structure 12 is in a quiescent state, e.g.,
when wheeled mobility device 10 is standing on a level horizontal
surface or tiltable stabilizing structure 12 or user support 14
otherwise have a target orientation, the representative plane 57 is
parallel to a target plane 52. For example, target plane 52 may be
horizontal, or have another orientation, that is preferred by a
user of wheeled mobility device 10. (For example, a particular user
may feel comfortable leaning slightly backward or forward, to the
right or left, or at another target orientation.)
[0086] Representative plane 57 may be understood to represent a
plane that is defined by swivel connection 28 and by displaceable
connections 16a and 16b. In this case, projected displaceable
connections 58a and 58b are identical with displaceable connections
16a and 16b, respectively, with the tilt of target plane 52
adjusted accordingly (e.g., target plane 52 may not be horizontal
when a component of wheeled mobility device 10, such as seat 36, is
to be maintained horizontal).
[0087] Alternatively, representative plane 57 may be defined such
that the tilt of target plane 52 is identical to the tilt at which
a component of wheeled mobility device 10, such as seat 36) is to
be maintained (e.g., as defined with respect to the local
horizontal and vertical). In this case, representative plane 57 of
tiltable leveling structure 12 may be determined by initially
defining a plane that is parallel to particular longitudinal axis
48 (e.g., an axis that is parallel to a projection of direction of
forward motion 42 into target plane 52) and that includes
displaceable connections 16a and 16b. Representative plane 57 then
is a plane parallel to this defined plane that includes swivel
connection 28. Projected displaceable connections 58a and 58b
represent projections of displaceable connections 16a and 16b,
respectively, into representative plane 57 along a line of
translation of each displaceable connection 16a or 16b. For
example, the line of translation of displaceable connection 16a or
16b may be the axis of its corresponding actuator shaft 62. Thus, a
displacement of projected displaceable connection 58a or 58b is
equal to a displacement of the corresponding displaceable
connection 16a or 16b.
[0088] In the configuration shown, swivel connection 28 is located
at or near a lateral midpoint of a front end of representative
plane 57, the front end being determined by direction of forward
motion 42. Projected displaceable connections 58a and 58b are
located near left and right corners, respectively, of a rear end of
representative plane 57. Other placements of swivel connection 28
and of projected displaceable connections 58a and 58b
(corresponding to other configurations of tiltable stabilizing
structure 12) may be provided.
[0089] A tilt of tiltable stabilizing structure 12 may be
characterized with reference to a target plane 52.
[0090] Representative plane 57 is characterized by longitudinal
axis 48 (substantially parallel to direction of forward motion 42),
and by lateral axis 44 (substantially perpendicular to longitudinal
axis 48). A tilt resulting from a rotation of tiltable stabilizing
structure 12 about lateral axis 44 with respect to target plane 52
may be quantified as pitch angle 46 (with value .theta..sub.P).
Similarly, a tilt resulting from a rotation of tiltable stabilizing
structure 12 about longitudinal axis 48 with respect to target
plane 52 may be quantified as roll angle 50 (with value
.theta..sub.R). Values .theta..sub.P of pitch angle 46 and
.theta..sub.R of roll angle 50 may be measured by inertial
measurement unit 40, or by a similar sensor.
[0091] Swivel connection 28 is located a constant distance 54 (with
constant value H.sub.0) from chassis floor 24. Distance 54 is
sufficient such that when chassis 11 or wheeled mobility device 10
standing or travelling over a surface that is sloped within a
predetermined range of slopes, projected displaceable connections
58a and 58b (and displaceable connections 16a and 16b) may be moved
toward chassis floor 24 so as to maintain representative plane 57
in an orientation that is parallel to target plane 52. For example,
a maximum slope that is to be accommodated by motion of
displaceable connections 16a and 16b may be a maximum slope upon
which wheeled mobility device 10 may safely travel.
[0092] Each of projected displaceable connections 58a and 58b is at
a variable distance 56a or 56b, respectively (with changeable
values H.sub.1 and H.sub.2, respectively, e.g., within the range
zero to 2H.sub.0), from chassis floor 24. Variable distance 56a,
56b, or both, may be changed by operating one or more actuators 60.
In FIG. 3C, projected displaceable connection 58 represents a point
where a line through projected displaceable connections 58a and 58b
intersects the plane of the section shown in FIG. 3C. Projected
displaceable connection 58 is at a distance 56 from chassis floor
24.
[0093] An iterative control algorithm may be applied by processor
25 to control operation of actuators 60 via motor control 27.
[0094] FIG. 4 is a flowchart depicting a method for controlling a
tiltable leveling structure of a wheeled mobility device, in
accordance with an embodiment of the present invention. FIG. 5 is a
block diagram of a control algorithm of the method depicted in FIG.
4.
[0095] It should be understood, with respect to any flowchart or
block diagram referenced herein, that the division of the
illustrated method into discrete operations represented by blocks
of the flowchart or block diagram has been selected for convenience
and clarity only. Alternative division of the illustrated method
into discrete operations is possible with equivalent results. Such
alternative division of the illustrated method into discrete
operations should be understood as representing other embodiments
of the illustrated method.
[0096] Similarly, it should be understood that, unless indicated
otherwise, the illustrated order of execution of the operations
represented by blocks of any flowchart referenced herein has been
selected for convenience and clarity only. Operations of the
illustrated method may be executed in an alternative order, or
concurrently, with equivalent results. Such reordering of
operations of the illustrated method should be understood as
representing other embodiments of the illustrated method.
[0097] Tilt control method 100 may be executed by processor 25 of
wheeled mobility device 10. For example, tilt control method 100
may be executed continually while power source 21 is switched on,
while wheel drive 23 is operating, upon operation of a user control
34 to move or change a configuration of wheeled mobility device 10,
or in response to another predetermined event or condition.
[0098] One or more algorithm parameters 210 used in application of
a control algorithm 200 may be predetermined or predefined (block
110). Such algorithm parameters 210 may include one or more gain
factors, one or more factors related to operation of actuators 60,
or other parameters used in application of control algorithm 200.
For example, the parameters may include gain adjustment factors
K.sub.P and K.sub.R, exponents p and r, length conversion factor
.DELTA., or other parameters that are utilized during application
of control algorithm 200 as described below. Algorithm parameters
210 may be defined, for example, during development of a model of a
wheeled mobility device 10, during production, adjustment,
maintenance or calibration of a particular wheeled mobility device
10, or otherwise. Algorithm parameters 210 may be adjusted in
accordance with preferences of a user of a particular wheeled
mobility device 10. For example, algorithm parameters 210 may
affect smoothness or jerkiness of motions, preferred speed of
motion, another user preference, or another characteristic of
operation of wheeled mobility device 10.
[0099] One or more target plane parameters 215 may be predetermined
or predefined for characterizing target plane 52 (block 115).
Target plane parameters 215 may include roll and pitch angles, or
other parameters that define target plane 52. For example, target
plane parameters 215 may be defined during calibration, adjustment,
or maintenance of a particular wheeled mobility device 10, during
adaption of a particular wheeled mobility device 10 to a particular
user, or at another time.
[0100] Target plane parameters 215 may include, for example, a
target pitch angle .THETA..sub.P and a target roll angle
.THETA..sub.R. For example, .THETA..sub.P=0 and .THETA..sub.R=0 may
indicate that tiltable leveling structure 12 and representative
plane 57 are to be maintained horizontal. Values of
.THETA..sub.P>0 may indicate a preference for a backward tilt,
while .THETA..sub.P<0 may indicate a preference for a forward
tilt. Tilt control method 100 is configured to adjust a tilt of
tiltable stabilizing structure 12 with the goal of maintaining
representative plane 57 parallel to target plane 52.
[0101] Execution of tilt control method 100 includes a series of
iterations. During each iteration, operation of actuators 60 is
controlled in accordance with measurements and calculations that
are made during that iteration. In the following, each iteration is
numbered with an index i.
[0102] Measured values of tilt angles of tiltable leveling
structure 12 at the current iteration i may be obtained (blocks 120
and 220). For example, the measured tilt angles may include pitch
angle .theta..sub.P(i) and roll angle .theta..sub.R(i), or another
set of angles that defines a tilt of tiltable stabilizing structure
12. The tilt angle measurements may be received from inertial
measurement unit 40, or from another sensor. Alternatively or in
addition, the tilt angle measurements may be obtained by analysis
of received signals that indicate one or more measured quantities
that are related to the tilt angles.
[0103] A displacement of each of displaceable connections 16a and
16b to be applied during the current iteration may be calculated
based on a deviation of the measured (block 130). In some cases,
the calculation may be considered to include the following
steps:
[0104] A deviation .epsilon..sub.P=.theta..sub.P(i)-.THETA..sub.P
of measured pitch angle .theta..sub.P(i) from target pitch angle
.THETA..sub.P may be calculated. A pitch gain factor G.sub.P(i) may
be calculated as
G.sub.P(i)=sign(.epsilon..sub.P(i))K.sub.P|.epsilon..sub.P(i)|.sup.P,
where K.sub.P is a multiplicative factor and p is an exponent
(block 230a).
[0105] The gain may be converted to pitch deviation distance
D.sub.P(i) by multiplying pitch gain factor G.sub.P(i) by length
conversion factor .DELTA.:
D.sub.P(i)=G.sub.P(i).DELTA.(block 240a).
[0106] Similarly, a deviation
.epsilon..sub.R=.theta..sub.R(i)-.THETA..sub.R of measured roll
angle .theta..sub.R(i) from target roll angle .THETA..sub.R may be
calculated. A roll gain factor G.sub.R(i) may be calculated as
G.sub.R(i)=sign(.epsilon..sub.R(i))K.sub.R|.epsilon..sub.R(i)|.sup.r,
where K.sub.R is a multiplicative factor and r is an exponent
(block 230b).
[0107] The gain may be converted to roll deviation distance
D.sub.R(i) by multiplying, roll gain factor G.sub.R(i) by length
conversion factor .DELTA.:
D.sub.R(i)=G.sub.R(i).DELTA.(block 240b).
[0108] A displacement of each of displaceable connections 16a and
16b in order to correct the deviations .epsilon..sub.P and
.epsilon..sub.R(i) may be calculated on the basis of the deviation
distances D.sub.P(i) and D.sub.R(i) (block 250). The calculated
displacements are configured to reduce the values of
.epsilon..sub.P(i) and .epsilon..sub.R(i) at the start of the next
iteration (e.g., in the absence of any further change in the tilt
of chassis 11 such as would be caused, e.g., by a change in slope
of terrain or another surface that supports wheeled mobility device
10) to a value that is close to zero.
[0109] The displacements may be calculated as linear combinations
of the deviation distances D.sub.P(i) and D.sub.R(i). For example,
displaceable connection 16a (and, equivalently, projected
displaceable connection 58a), at current distance H.sub.1(i) from
chassis floor 24, may be displaced such that:
H.sub.1(i+1)=H.sub.1(i)-D.sub.P(i)D.sub.R(i).
[0110] Similarly, displaceable connection 16b (and, equivalently,
projected displaceable connection 58b), at current distance
H.sub.2(i) from chassis floor 24, may be displaced such that:
H.sub.2(i+1)=H.sub.2(i)-D.sub.P(i)-D.sub.R(i).
[0111] The displacements of H.sub.1 and H.sub.2 may be expressed in
units of length (e.g., millimeters or centimeters), a rotation
angle or number of rotations of actuator 60 (e.g., turning a screw
of a screw mechanism, as shown, a screw of a scissor jack
mechanism, an eccentric disk, or another mechanism for converting
rotation of a motor to linear motion), or otherwise.
[0112] The actuator 60 associated with each of displaceable
connections 16a and 16b be operated to achieve the calculated
displaced distances from chassis floor 24, H.sub.1 (i+1) and
H.sub.2(i+1), respectively, during the current iteration (block
140).
[0113] For example, a speed and direction of operation of each
actuator 60 may be controlled (e.g., via operation of motor control
27) to achieve the calculated displaced distance by the start of
the following iteration (returning to blocks 120 and 220). In some
cases, the speed of operation of each actuator 60 may be limited
such that a rate of tilting of tiltable leveling structure 12 is in
the range 1 degree per second to 10 degrees per second, e.g., about
4 degrees per second.
[0114] When one or both of exponents p and r are greater than zero
(e.g., p=r=2, or p or r being equal to another positive number),
such that the absolute value of .epsilon..sub.P and .epsilon..sub.R
is raised to a positive power, the calculated deviation distances
D.sub.P and D.sub.R are proportionally greater for greater measured
deviations .epsilon..sub.P and .epsilon..sub.R than for smaller
deviations. In this case, the changes in distances H.sub.1 and
H.sub.2 during a single iteration are larger for large deviations
than for small deviations. Thus, in the case of a large deviation,
the orientation of tiltable leveling structure 12 is rapidly
returned to that of target plane 52. Such rapid return to the
target orientation may enable wheeled mobility device 10 to travel
safely over surfaces of varying slope. One the other hand, when the
deviations are small, the tilt of tiltable stabilizing structure 12
is varied slowly, enabling a smooth ride for the user of wheeled
mobility device 10. In this case, the control loop may be described
as having an adaptive bandwidth: wider for larger errors and
narrower for smaller errors.
[0115] On the other hand, when the values of the exponents are
zero, p=r=0, the calculated deviation distances D.sub.P and
D.sub.R, and thus the changes in distances H.sub.1 and H.sub.2, are
independent of deviations .epsilon..sub.P and .epsilon..sub.R.
[0116] Values of exponents p and r, as well as those of factors
K.sub.P, K.sub.R, and .DELTA., may be selected in accordance with
one or more of properties or characteristics of a particular or
representative wheeled mobility device 10, of a preference of a
particular or representative user of wheeled mobility device 10, or
otherwise.
[0117] A user self-leveling apparatus for wheeled mobility device
10 and a tilt control method 100, in accordance with an embodiment
of the present invention, may be advantageous over other types of
self-leveling systems. In particular, the mechanism for tilting
tiltable stabilizing structure 12, using linear actuators and a
fixed swivel connection 28, may be advantageous over double-gimbal
mechanism with angular actuators for producing two mutually
orthogonal rotations.
[0118] For example, the mechanism for tilting tiltable leveling
structure 12 may occupy less space, require less maintenance, and
may be less expensive than a typical double-gimbal mechanism.
Actuators 60 produce linear translation only and are not orthogonal
to each other (such that movement of each of displaceable
connections 16a and 16b affects both roll and pitch), For example,
control algorithm 200 may be robust, simpler, and more easily
configured than an algorithm for controlling a double-gimbal
mechanism. The control algorithm 200 is configured to always
converge to the orientation of representative plane 57 that of
target plane 52, even in the presence of small mechanical
inaccuracies such as backlash.
[0119] Control algorithm 200 may be advantageous over other
algorithms (such as PID) due to its simplicity, smooth operation,
and robustness. Application of an adaptive control-loop, as in
application of control algorithm 200, may prevent overshooting,
undershooting, and limit-cycle phenomena.
[0120] Different embodiments are disclosed herein. Features of
certain embodiments may be combined with features of other
embodiments; thus certain embodiments may be combinations of
features of multiple embodiments. The foregoing description of the
embodiments of the invention has been presented for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise form disclosed. It should
be appreciated by persons skilled in the art that many
modifications, variations, substitutions, changes, and equivalents
are possible in light of the above teaching. It is, therefore, to
be understood that the appended claims are intended to cover all
such modifications and changes as fall within the true spirit of
the invention.
[0121] While certain features of the invention have been
illustrated and described herein, many modifications,
substitutions, changes, and equivalents will now occur to those of
ordinary skill in the art. It is, therefore, to be understood that
the appended claims are intended to cover all such modifications
and changes as fall within the true spirit of the invention.
* * * * *